Padded sound reproducing horn



.Patented .lune 2, 1931 UNITED STATES 'PATENT OFFICE LEONARD L. MAXAM, 'OF .SAN PEDRO, CALIFORNIA, ASSIGNOR OF ONE-THIRD T0 A CLARENCE S. CREWS, OF SAN PEDRO, CALIFORNIA PADDED SOUND REIRODUGING HORN Application led .Tune 19,

This 'invention relates to sound reproducing instruments. f t An object of the invention is the production of a sound reproducer of the type ordinarily termed loud speakers'which is caable of reproducing sound with extreme delity as to tone quality. Another Object is the production of a loud speaker having an extremely natural ytone as described, in which the tone ,fidelity is attained without sacrifice of volume.

A further object is the provision of improvements in that class of loud speakers,

which is ordinarily employed in theaters and the like, to reproduce sound accompanying the action depicted cinematographically.y

Another object is to` provide a very simple means of improving the tone qualities of the conventional sound reproducer, and more particularly of the class of sound reproducers employed for use in conjunction with sound pictures. v

A still further object is the provision of means for improving the tone of -a loud speaker, this means being of a very simple nature and may very easily be applied to those sound reproducers already in service, and 'at a relatively small cost.

A further object is the provision of improvements in soundreproducing horns,

. which may be employed to correct discrepancies between the tonal characteristics of each of a plurality of horns.

1929. Serial No. 371,995.

The plane of section is taken upon the line l-l of Fig. 2, and the direction of'view is indicated by the arrows:

Fig. 2 is a transverse, vertical sectional view taken upon the line 2-2 of Fig. l, with the direction of View as indicated by the ployed for the reproduction of the sound accompanying the cinematograph depiction of actlon. In the construction of this type of sound reproducing instrument, considerable efl'ort has been expended toward the accurate reproduction of sound throughout vthe entire audio range. Particular emphasis hasbeen laid upon the reproduction of sound of the lower registerjf To such an extent has this effort been'carried, that in the Kcase of many of the loud speakers now in use, the notes of the lower register are overemphasized, resulting in a distortion of the ultimate sound characterized by unnatural rumbling; `Particularly true is this when it is necessaryto provide for relativelygreat amplification of sound-as for example, in the case-of sound pictures.

Loud speakers employed for this service, are frequently assembledinto a bank of -four or more, each a complete reproducing instrument; but all of them receiving the same electrical energy and from the same translating apparatus whereby this electrical energy is derived from light energy or y some other source. Such a bank of speak- `ers is arranged closely behind the tion screen, the speakers being so rojec'- stributed Athat the sound emanating therefrom is not centralized, i. e., the sound appears to the audience upon the opposite side of v the screen, to emanate from the entire area f register with the amplifying elements of the speakers through which the sound may pass unrestrictedly.

Describing the `invention in one of itsy several possible embodiments, the figures of 1 the drawings disclose a sound reproducer composed of a pair of loud speakers 5 and 6. Each speaker is composed of an electrical unit 7 and 8 respectively, whereby electrical energy isA translated to sound vibrations and, an amplifying unit in the form of tortuous horns 9 and 11 respectlvely. Each horn includesa mouth or bell end 12 in communication through x the throat portion 13, with the smaller end 14 to which thev unit 7 or 8, as the case may be, is connected. Each horn is so designed that its air column16 gradually increases in cross sectional area from the small end of the horn, to the bell end 12.

The speakers 5 and 6 are suitably supported upon a' framework-indicated in its entirety at 17, and are so arranged that the sound emanates'from the speakers in convergent lines, i. e., the upper speaker is directed slightly downwards, while the lower speaker is directed angularly upwards as clearly shown upon Fig. 1. The frame 17 ordinarily consists of vertical corner posts 18, and longitudinally and transversely extending horizontal braces 19 and 20 respecf tively. These members may be composed of any suitable stock such as angle iron suitably riveted or otherwise 'securely fastened together. in proper assembled lrelationship.

`Heretofor'e, the frame 17 of such a bank of speakers, was left open. My invention contemplates the provision of suitable front,`

back, side, top, and bottom partitions 21, 2 2, 23, 24, and 26 respectively. .These partitions are composed of any suitable sound vibration dampening material such as felt, sheets of cotton batting or the like; and are`soarranged that they completely encase the several speakers 5 and 6,) with the exception that the front partition 21 is provided with lan aperture 27 in register preferably of the same material as that of which the partitions are composed. These coverings are secured to the horns 9.and 11 in such position that they completely cover all surfaces of the horns preferably bothl inside and out, adjacent the bell end thereof,

and extend downwards into the throat thereof vas clearly shown upon Fig. 1. The coverings may be attached to the horns 'in any suitable manner such as by the use of any suitable adhesive, and extend down into the throats of the horns as far as convenient, taking into considerationft-he tortuous nature ofthe throats., Furthermore, a sheetv 29 of similar sound dampening material extends between the extreme ends of the bells 12 of both horns 9 and 11.

l It has been found in actual operation that when a bank of speakers'similar to that described above, is employed without the4 paddmg or partltlons of sound dampemng material, the horns 9 and 11 themselves, are set into vibration in resonance` with the vibration of the air columns. The production of unnatural tones such as the low rumbling so frequently present in the sound produced by amplifying devices of this general character, is largely attributable to this phenomenon, inasmuch as the vibration of the material of which the horns themselves are composed, interferes 'with the normal 100 vibration of the air column. This accounts for the improvement in the tone accomplished by providing the linings and partitions above described, inasmuch as they dampen the vibrations as they approach the horns and thus largely prevent the horns being set into vibration, thereby enabling the sound vibrations of the air column itself, to issue from the bell of the horn undistorted and without the development of any sound interference.

A bank of speakers such as that above described, is conventionally employed by being positioned closely behind the projection screen. Consequently, each bank is 11`5 tions issuing from the bells of the horns, are found to impinge against the back of the screen and rebound partially at least, back into the horns themselves.l In this manner, additional sound interference has been developed through the reverberation of 4the 125 sound reflectingfrom the after side of the screen,l intermingling with the sound issuing direct] -from the horns. The linings 28 upon t e interior surfaces of the horns, is

found to eliminate this undesirable condialso catches and dampens a largeamount of these reflected sound waves. Furthermore, the partitions 21, 22, 23, 24, and 26, intercept the remaining portion of these reflected sound waves, as well as sound waves emanating from other sources, which are apt to impinge upon the otherwise unprotected horns 4to develop unpleasant and undesirable vibrations thereof. Y

It has been found that the provision of the linings and partitions as above described, upon ya conventional bank of loud speakers, results in the production of sound having remarkable fidelity of tone even though amplified to a very great extend. While the .notes of the lower register, as well as the higher notes, are reproduced with a high degree of perfection, the rumbling as well as other distortion so frequently developed in speakers of this general class, is largely, if not completely eliminated; with the result that any sound reproduced by such a bank of `speakers Whether instrumental music or the voice, in either speaking or singing, is reproduced with a lhigh degree of accuracy.

I have found that the improvements constituting the present invention, are also of extreme value in connection with the banks or towers of sound reproducing instruments which are conventionally employed to reproduce the sounds `accompanying cinematographically depicted action, inasmuch as they permit of accurate adjustment -of the padding upon each of the several horns of a tower, so as to cause each reproducing horn to have exactly the same tonal characteristics as the other horns of the same bank. In manufacturing these loud speakers, every effort is expended to cause the several speakers of av bank to have exactly the same tonal characteristics; but owing to the exigencies of manufacture, such as variation in the quality of the wood employed in the construction of-the horns, and other variations in quality of' material and the like, detection of which is impossible, it is practically beyond possibility to so construct the horns that they all have exactly the same tone. However, by varying the quantity and positioning of the padding when adapting the improvements of the present invention to the several speakers of a bank, these inherent discrepancies of tonal characteristics may be very nearly, if not completely eliminated; with the ,result that the sound emanating from each of the several speakers of the bank, blends perfectly with that from the other speakers, at least with such a degree of nicety Ithat any variation between their respective sound outputs, can not be detected bythe ear. v f

- It is to be understood that the` details of the invention asl-herein disclosed, are subject to alteration within the spirit or scope of rrthe appended claims.

I claim:

1. A loud speaker comprising a frame, a i.

sound reproducer mounted thereon and including va sound amplifier, and a covering of vibration dampening material carried by said frame andcompletely enclosing said reproducer with the exception of an opening therein in register with said amplifier.

2.A loud speaker comprising a frame, a sound reproducer mounted therein and including an amplifying horn, a coveringof vibration dampening material carried by the frame, said covering encasing said reproducer and having an aperture therein in register with the bell end of said horn, and a sheet of vibration dampening padding material covering the surfaces of said horn adjacent the bell end thereof and otherwise exposed to sound vibration.

' 3. A loud speaker comprising a frame, a plurality of soundt reproducers mounted thereon, leach including an amplifying horn, a covering of vibration dampening" material carried by said frame, said covering completely encasing said reproducers with the exception of an aperture therein in register with the bell ends of said horns, and sheets of vibration dampening material covering surfaces of said Vhorns adjacent the bell `ends thereof otherwise exposed to ,sound vibration. f

4c. A loud speaker comprising a frame, a

plurality of sound reproducers mounted thereon, each including an amplifying horn,

tion dampening housing therefor comprising a framework and sheets of padding material stretched upon said framework about said reproducer, said Jpadding material engaging the edges of said horn to completely close the spacel defined by said framework.

V6. In a loud speaker, a sound reproducer comprising an amplifying horn, and a vibration dampening housing therefor comprising a framework, sheets of padding material stretched upon said framework about said reproducer, said padding material engaging the edges of said horn `to completely close the space defined by said framework, and

padding secured to the inside of said horn and extending from the outer edges thereof l back into the throat thereof.

7. In a loud speaker, a sound vreproducer comprising an amplifying horn, anda vibration dampenjng housing therefor comprising a framework, sheets of padding material stretched upon said framework about said reproducer, said padding material engaging the edges of said horn 'to completely close the space defined by said framework, padding secured to the inside of said horn and extending from the outer edges thereof back into the throat thereof, and padding secured to the exterior surface of said horn throughf out substantiallyv the 'entire area thereof.

In testimony whereof I have signed my name to this speciication.

LEONARD L'. MAXAM. 

